GERMINATION AND GROWTH. 



151 



Ustilago as have been remarked in the sporules of the first 

 generation in Tilletia. 



Returning to Cystopus, as the last of the Uredines, we must 

 briefly recapitulate the observations made by Professor de Bary,* 

 who, by the bye, claims for them an affinity with Pcronospora 

 (Mucedines but too well known 

 in connection with the potato 

 disease), and not with the Ure- 

 dines and their allies. In this 

 genus there are two kinds of 

 reproductive organs, those pro- 

 duced on the surface of the plant 

 bursting through the cuticle in 



White pustules, and which De Fig. 90.-Pseudospore of Usjilapo rtctp- 

 Bary terms COnidia, which are t"-culorum in germination, and secondary 

 . -, . , . , , . spores in conjugation. (Tul.) 



generated in chains, and certain 



globose bodies termed oogonia, which are developed on .the 

 mycelium in the internal tissues of the foster plant. When the 

 conidia are sown on water they rapidly absorb the moisture, and 

 swell ; the centre of one of the 

 extremities soon becomes a large 

 obtuse papilla resembling the 

 neck of a bottle. This is filled 

 with a granular protoplasm, in 

 which vacuoles are formed. 

 Soon, however, these vacuoles 

 disappear, and very fine lines of 

 demarcation separate the pro- 

 toplasm into from five to eight Fio. 91.— Conidia and zoospores of &»- 

 . , , . . . topue candid its ; a. conidium with the 



polyhedriC portions, each, pre- plasma divided ; b. zoospores escaping ; 

 i. „ rui v • (.1 l J c - zoospores escaped from the coDidium; 



Sentmg a little tainfcJy-COlOUred rf. active zoospores; e. zoospores, having lost 



vacuole in the centre (a). Soon thoir cma - commencing to germinate, 

 after this division the papilla at the extremity swells, opens itself, 

 and at the same time the five to eight bodies which had formed 

 in the interior are expelled one by one (b). These are zoospores, 



* De Bary, " Recherches," &e. in " Annales des Sciences Naturelles " (4™ 

 sir.), xx. p. 5 ; Cooke in " Pop. Soi. Rev." iii. (1864), p. 459. 



